1. Field of the Invention
The invention relates to a semiconductor process.
2. Description of Related Art
With advancement of technologies, the level of integration of electronic devices tends to be raised, so as to comply with current demands for lightness, thinness, shortness, and smallness. In order to improve the level of integration, not only dimensions of semiconductor devices can be reduced, but also the distance between semiconductor components can be decreased. Nevertheless, either the size reduction of the semiconductor devices or the decrease in the distance between the semiconductor components may result in certain issues.
In general, in the fabrication of the gates, an ion implantation process is applied to define a spacer oxide layer or a gate oxide layer. For example, after an opening is formed in a material layer, the surface of the opening is doped by an ion implantation process. Then, a converting process (i.e. an oxidation process) is performed on the surface of the opening to form a converting layer (i.e. an oxide layer) thereon, and a conductive material is filled in the opening to form a gate. However, the scattering effect is likely to occur in the ion implantation process due to the decrease of the dimensions of the opening, and therefore the doping profile is difficult to control. That is, in the side wall of the opening fabricated as described above, the doping depth of an upper portion and a lower portion is different. Therefore, the converting layer subsequently formed on the side wall of the opening may have non-uniform thickness, and the insulation effect of the converting layer is negatively affected.